This disclosure generally relates to convex, three dimensional mirrors and, more particularly, to a mirror, sometimes referred to as a “cross-over” or “cross-view” mirror, which affords a bus driver, for example, a school bus driver, visual access in front of, as well as alongside the bus. Such cross-over mirrors can however also be used at the rear or front corners of other vehicles such as with trucks, mail vans and the like. More specifically, the present disclosure relates to non-ellipsoidal, asymmetric cross-view mirrors which are optimized to produce more distinct images of objects located in front of or alongside a school bus or similar vehicle.
For many decades, cross-over mirrors and mirror assemblies have been deployed on school buses, and are in fact required by federal and local regulations. A substantial body of prior art has been published describing various mirrors of the type to which the present invention relates. Prior art mirrors include both circular and ellipsoidal mirrors. The prior art ellipsoidal mirror lenses have been characterized by radii of curvature (measured along planar cross-sections on the major and minor axes) which were distinctly non-constant, i.e. tending to increase or decrease on the mirror lens toward or adjacent its peripheral, circumferential edge. The variation in the radius of curvature is used to obtain larger and less distorted images at the mirror center, and smaller, but more distorted, images, at the peripheral regions on the mirror. This, in essence, would increase the field of view that the mirror monitors in and around the school bus.
However, it has been determined that the size and general shape of the monitored area in front of a school bus, differs from that which needs to be monitored alongside the bus. That is, school buses and similar vehicles have comparative lengths several times larger than the widths of the vehicles. The image of a child standing alongside a school bus near the rear wheels needs to be sufficiently large to afford the driver a good view of a child who may stoop low or fallen or slipped under or too close to the school bus. At the front of the bus, it has been determined, is more important to assure that the entire width and several feet in front of the bus are clearly visible. In other words, the field of view characteristics in front of the school bus and alongside differ from one another. Prior art mirrors have not been optimized to fully accommodate these differences.
Rather, all prior art mirrors, including those that have horizontally stretched bodies, are widthwise symmetrical with respect to their generally vertical mounting axis. Thus, the mirror surface size and shape and field of view to the right of the axis is identical to the mirror surface and view to the left of the axis. Therefore, both sides of the lens provide the same image reflecting characteristics at the left mirror side, which is primarily focused on the area in front of the bus, as at the right mirror side which focuses images from alongside the bus (for a mirror mounted to the right of the driver).
In addition, prior art mirrors that have varying radii of curvature over the entire mirror surface or substantial part thereof result in continually changing image sizes, along the surfaces of the mirror. This can make it more difficult for the driver to follow and carefully monitor the movements of a child alongside or in front of the school bus.